BIOL 2401 A&P I Lecture Notes Muscular System : Gross Dr. Weis
MUSCULAR SYSTEM
Skeletal muscles
involved with locomotion, posture, support, protection
attached to skeletal muscle at a certain point that will determine the movement produced, so
the skeleton becomes the lever and the joint is the point or region of action at which the movement by the muscles is accomplished
.
Lever Systems :
Lever --> rigid bar (bone)
Fulcrum --> region of action (joint)
Effort --> applied force (muscle contraction)
Load --> resistance (what is moved, ie, bone/tissue)
Lever systems have three classes : First, Second,
Third class
First Class :: see saw
fulcrum in center, between effort and load
mechanical advantage
Second Class :: wheelbarrow
fulcrum at one end, closer to load
mechanical advantage
Third Class :: shovel
fulcrum at one end, closer to effort
mechanical disadvantage, speed advantage
most common class
To summarize,
if effort farther than load from fulcrum, then there is a mechanical advantage, also called a power lever
if effort nearer than load to fulcrum, then there is a mechanical disadvantage, also called a speed lever
Position of the three elements (load, force, pivot point) will affect
:
1) speed of contraction
2) range of movement
3) weight that can be lifted
Muscle terminology
Skeletal muscle will usually
1. begin at a tendon, called the ORIGIN
2. end in a tendon, called the INSERTION
3. Have a specific action
4. Innervated by a specific motor nerve
5. Antagonist opposes or reverses movement
6. Synergist promotes same movement
Naming muscles can be related to :
1. Fiber Direction ---> straight, oblique, transverse
2. Actions produced --> extensor, flexor, rotator, abductor, adductor
3. Regions of the body --> ribs, scapula, head, femur, tibia, ulna, abdomen
4. Characteristics --> a. Number of heads ( #2,3,4) b. Shapes....diamond, triangle, circle
c. Description... great, deep d. Size ... large, small, short
5. Divisions on skeleton....axial, appendicular
I. Axial Musculature
A. Muscles of the Head & Neck
B. Muscles of the Spine
C. Muscles of the Thorax and Abdomen
D. Muscles of the Pelvic floor
A. Muscles of the Head and Neck
1. Muscles of facial expression
2. Muscles of the eye
3. Muscles of mastication
4. Muscles of the tongue
5. Muscles of the larynx
6. Muscles of the neck
1. Muscles of Facial Expression
a. Nerve supply : Cranial Nerve 7
b. Action : mouth....move lips, associated with the skin,
so as these muscles contract, the skin also moves
nose....nasalis muscle
ear... movement
scalp...movement of forehead/eyebrow`
eye...movement of the eyelid, Raise eyelids CN 3
levator palpebral muscle, Close eyelids CN 7
orbicularis oculi muscle
c. Bones involved :
mouth....mandible, maxilla
nose....skull, nasal bone
d. muscles to know
occipitalis, frontalis, orbicularis oculi,zygomaticus, risorus, orbicularis oris,
mentalis, buccinator, levator palpebrae, platysma
2. Muscles of the Eye
Oculomotor muscles, straight muscles, #6
a. Nerve supply : CN 3,4,6
b. Action : lateral, medial, up, down, rolling
c. postions of these muscles
lateral, medial, superior, inferior RECTUS
obliques (superior, inferior)
3. Muscles of Mastication
a. Nerve : CN 5, the mandibular branch of the trigeminal nerve
b. Action : on the jaw to open, close, protract, primarily on elevating the mandible
c. Bone : mandible for insertion
d. Muscles : masseter, temporalis, pterygoid :medial and lateral, digastric
(feel these muscles when you chew)
4. Muscles of the Tongue
a. Nerve : CN 12 (Hypoglossal)
b. Action : to move the tongue
c. Bones : Hyoid, mandible, soft palate, temporal
d. Muscles: genioglossus, hyoglossus, styloglossus
5. Muscles of the Larynx
a. Nerve : CN 5, 7, 12
b. Action : move larynx
c. Bones : hyoid, clavicle, larynx cartilage
d. Example :
these muscles are named for the region
____________hyoid
e. Muscles : stylohyoid, mylohyoid, geniohyoid, sternohyoid, sternothyroid, omohyoid, thyrohyiod
Also note that the digastricus and the mylohyoid muscles depress the mandible (close the jaw)
6. Muscles of the Neck
a. Nerve : CN XI, cervical spinal nerves
b. Action : flex, rotate neck
c. Bones : sternum, clavicle, ribs
d. Muscles : sternocleidomastoid, scalenes
B. Muscles of the Spine
a. Nerve : spinal nerves at regional location, cervical, thoracic, lumbar
b. Action : move spinal column
c. Examples
1. Extensors
a. Spinalis at spinous processes of vertebra
b. Longissimus @ transverse processes of the vertebrae
c. Iliocostalis... associated with the ribs from different vertebral regions
2. Flexors
associated with the transverse process of the cervical, thoracic vertebrae
and the bodies and transverse processes of the lumbar vertebrae.
Quadratus lumborum
C. Muscles of the Thorax and Abdomen
a. Nerve : branches of the regional spinal nerves
Thorax... associated with movement of the ribs intercostal muscles (internal, external)
... Rectus group --> Diaphragm
Nerve : phrenic n.
Action: expand thoracic cavity compress the abdomen
Abdomen... three layers, compress abdomen
1. External oblique
2. Internal oblique
3. Transverse abdominus
..Rectus Group --> Rectus Abdominus
extends from the Xypoid process to the symphysis pubis
divided by the linea alba (white line)
action : flexes the vertebral column
Hernias
def. : protrusion of an organ through an abnormal opening
examples : inguinal, diaphragmatic
related to hereditary factors
inguinal hernias through the inguinal ring formed by the abdominal muscles, assoc. with the External Abd. oblique m.
D. Muscles of the Pelvic Floor (Perineum)
* Pelvic Diaphragm
* Urogenital Diaphragm
a. Nerve : Pudendal n., sacral n.
b. Action : on genitalia, urethra, anus
c. Bones : ischium, coccyx
and tendons. ( will be studied with the digestive and reproductive systems)
d. Muscles : levator ani, sphincter urethrae, external anal sphincter
II. Appendicular Musculature
A. Shoulder and Arms
B. Legs
A. Muscles of the Shoulder and Arm
1. Shoulder
2. Upper Arm
3. Forearm and wrist
4. Palm and fingers
1. Shoulder
a. Nerves : Scapular N., CN 6, Long Thoracic n.
b. Action : Move scapula, shoulder, neck
c. Bones :
origin : vertebrae, ribs, manubrium
insertion : scapula, clavicle
d. Muscles : trapezius, Rhomboideus, serratus anterior, levator scapulae, pectoralis minor
2. Upper Arm
a. Nerves : Scapular N. , Axillary N., Musculocutaneous N., Thoracodorsal N.
b. Action : movement of the Humerus
c. Bones :
orgin : scapula, sternum, spinal processes of the thoracic vertebrae
insertion : greater/lesser tubercle of the humerus, shaft of the humerus
d. Muscles :
Deltoid, Teres Major, Pectoralis major,
Supraspinatous, Infraspinatus, Subscapularis,
Latissimus dorsi, coracobrachialis, teres minor
3. Forearm and Wrist
a. Nerves : musculocutaneous , median, ulnar, RADIAL nerves
b. Action : movement of the forearm to flex, extend, pronate, supinate
movement of wrist to flex, extend, adduct, abduct
c. Bones :
origin : scapula, humerus
insertion : radius, ulna, metacarpals
d. Examples :
Biceps brachii...flexors, musculocutaneous n.
Triceps brachii... extensors, Radial n
Brachialis, Brachioradialis, pronator teres,
Flexor carpi's (ulnaris, radialis ) --> median & ulnar nerve
Extensor carpi's (radialis, ulnaris ) -- > median & ulnar nerve
4. Palm and Fingers action involves the tendons that pass from the extensors and flexors
Muscles : flexor digitorum, extensor digitorum, abductor polllicus longus
B. Muscles of the Legs
1. Thigh
2. Lower leg
3. Ankle, foot, toes
1. Thigh
a. Nerve : gluteal, obturator, SCIATIC, FEMORAL
b. Action : movement of the thigh
rotate medially, laterally
flex & extend, ab/ad duct
c. Bones :
origin ilium and obturator foramen of os coxa sacrum, vertebrae
insertion ... Femur (greater & lesser trochanter)
d. Muscles : gluteal group (maximus, medius, minimus)
adductors (longus, brevis, magnus)
iliopsoas
obturators (for lateral rotation)
sartorius
pectineus
gracilis
2. Lower Leg
a. Nerve : SCIATIC, FEMORAL, Obturator
b. Action: thigh....flex, extend, rotate
leg...flex, extend
c. Bones :
origins.. ischium, pubis, femur
insertions.. femur, tibia
d. Muscles :
Knee extensors --> FEMORAL N.
(1) Quadriceps : Rectus femoris and Vastus Muscles (#3)
Vastus medius, vastus lateralis, vastus intermedius
these muscle tendons insert upon the patella
and the patellar ligament inserts on the tibial tuberosity.
(2) Tensor fasciae latae
Leg flexors
Hamstrings : Biceps femoris
Semimembranosis
Semitendinosis
Nerve : Sciatic n.
Gracilis m
Sartorius m.
3. Ankle, Foot, Toes
a. Nerve : Sciatic branches (peroneal, tibial)
b. Action :
foot --> dorsi & plantar flexion, adduction
toes --> dorsi & plantar flextion
c. Bones :
origin.. distal femur, tibia, fibula
insertion.. tarsals, metatarsals, phalanges
d. Muscles :
dorsiflexors of ankle....Tibialis anterior
plantar flexors of ankle...
gastrocnemius
soleus
these muscle tendons form the CALCANEON tendon that inserts on the calcaneous (a tarsal bone)
peroneus brevis
peroneus longus
flexor digit ...muscle, and the tendon of the peroneus brevis
extensor digit...muscle and the tendon of the tibialis anterior
Injuries to muscles/bones....primarily due to stress
1. Sprains : tear/break in tendon or ligament
2. Strains | tear/break in muscle
3. Tendinitis : Inflammtion of the connective tissues sheath of the tendon
4. Cramps : involuntary, painful muscle contraction
5. Bone fracture
6. Bone bruise
7. Compartment syndrome